System and method for event messages in a cache coherent interconnect

Abstract

A cache coherent interconnect connected to one or more agents, such as CPUs, GPUs, Peripherals, etc. using network interface units (NIUs), and having one or more internal modules, such as a directory, is provided with one or more event-to-message converters, and one or more message-to-event converters. When a particular event occurs within one of the agents or modules, a message is initiated and transmitted using the existing interconnect wiring to one or more agents or modules, which have associated NIUs, that need to be aware of the event. Response messages showing the status of the event-message may also be generated. Therefore, messages are sent when events occur, instead of constantly using bandwidth for status updates when no status is changing, making the interconnect more efficient and freeing up bandwidth. These converters are provided as additional hardware blocks incorporated into the various NIUs and modules.

What is claimed is: 
     
       1. A cache coherent network-on-chip (NoC) comprising:
 a transport interconnect; and 
 a plurality of network interface units (NIUs) in communication with the transport interconnect, 
 wherein each NIU is in communication with an agent and each NIU includes an event-to-message converter for converting events into messages and sending messages through the NoC and a message-to-event converter for receiving messages from the NoC and converting the messages into events, 
 wherein an originating NIU selected from the plurality of NIUs, in response to detecting an event, which is a state change in its respective agent, that is provided to as an input to the originating NIU that converts the event into a message using the originating NIU's event-to-message converter and the message is transmitted, using the transport interconnect, to at least one destination agent, which is in communication with a destination NIU that is selected from the plurality of NIUs, and 
 wherein a message-to-event converter at the destination NIU converts the message to a destination event that is passed on to the destination agent from the destination NIU. 
 
     
     
       2. The NoC of  claim 1 , wherein each message-to-event converter is in communication with the NoC and receives messages that are converted into events. 
     
     
       3. The NoC of  claim 1 , wherein the destination NIU, in response to receiving the message, generates a response message for transmission over the transport interconnect back to the originating NIU to acknowledging receipt of the event at the destination agent. 
     
     
       4. The NoC of  claim 2 , wherein at least one NIU includes at least one multiplexor to combine messages initiated by the event-to-message converter with other messages generated by the at least one NIU. 
     
     
       5. The NoC of  claim 4 , wherein the at least one NIU includes at least one demultiplexor that extracts messages received from the NoC, and directs extracted messages related to events from any event-to-message converter to the message-to-event converter of the at least one NIU. 
     
     
       6. A method of communication of events using a cache coherent network-on-chip (NoC), the method comprising:
 detecting an event at an agent, wherein the event is an indication of a state change in the agent and the event is communicated to other agents; 
 converting the event to an event message using an event-to-message converter at a network interface units (NIU) in communication with the agent; 
 transmitting the event message using the NoC regardless of domain parameters of the agent relative to a destination NIU; 
 receiving the event message at the destination NIU; and 
 converting, using a message-to-event converter at the destination NIU, the event message to a destination event. 
 
     
     
       7. The NoC of  claim 6 , wherein the destination NIU, in response to receiving the message, generates a response message for transmission over the NoC back to an originating NIU to acknowledging receipt of the event at the destination agent. 
     
     
       8. The NoC of  claim 6 , wherein at least one NIU includes at least one multiplexor to combine messages initiated by the event-to-message converter with other messages generated by the at least one NIU. 
     
     
       9. The NoC of  claim 8 , wherein the at least one NIU includes at least one demultiplexor that extracts messages, which are related to events sent from any event-to-message converter, and directs the extracted messages to the message-to-event converter of the at least one NIU.